This invention relates to an reinforced radiation detector comprising a pyroelectric detector element in a hermetically sealed housing.
Infrared radiation detectors comprising pyroelectric detector elements are often referred to briefly as pyroelectric detectors. Pyroelectric detectors are used for a variety of purposes, for example in remote switching systems, in intruder alarms, and in movement sensors generally. Such sensors rely on the fact that a human being naturally provides a moving source of infrared radiation as he walks about or even as he moves only part of his body, for example by waving his hand. The radiation which he emits is converted by the pyroelectric detector into an electric signal which can be used, for example, to actuate an alarm or to switch lights on or off.
Conventionally, the pyroelectric detector element is mounted in a hermetically sealed housing to shield it from environmental influences. The housing comprises a canister with an aperture which is closed by a window made of a material, such as silicon, which transmits the infrared radiation to be detected. Pyroelectric detectors in which the window is fixed over the aperture and inside the canister are disclosed, for example, in British patent application No. GB 2,133,615 and in British patent application No. 8332264 (corresponding to U.S. Pat. No. 4,616,136). In both cases, however, it is difficult to locate the window correctly over the aperture.